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9/19/2017 7:27:10 PM
Posted: 10/20/2003 4:21:50 AM EDT
Took my new M4forgery to a friend's place this weekend to do some sighting in and some plinking. About 17 rounds in on my first mag (20 rounder) the gun didn't fire. I cycled the action, saw a fresh round go into the chamber, and aimed again. Nothing. I could hear the hammer dropping, but no boom.

I then cleared the chamber and took out the mag. When I was doing that I heard something rattling inside of the gun. Oh great I thought, I got a POS and it already broke.

So I decided to break it down. I pop the rear take-down pin and the buffer and spring fly out of the buffer tube. Upon closer examination I found that the buffer retainer top had been stripped off and had gotten caught behind something because it was preventing the rifle from firing. I couldn't believe that it broke, but was relieved it was't anything else.

Well at that point I reassembled the rifle, holding the buffer and spring back into the tube and locked the upper back into place. I fired the rifle three times like this (no buffer retainer).

My questions are these:

1. What could have caused the buffer retainer to break like that? (i.e. fubar assembly, bad part, etc.)

2. Is firing the rifle without the retainer bad, as in is it causing extra bolt/extractor wear? Could it cause a slamfire or some other malfunction?

Rifle info:
DPMS Lower with,
J&T M4 parts kit. This includes a fake M4 6 pos. buttstock and a "tach brake" muzzle brake.

Ammo - Federal Lake City XM193 lot 45.

Assembled by me.
Link Posted: 10/20/2003 4:54:36 AM EDT
The buffer retainer is absolutely non-essential. It is just a convenience to hold the buffer in place while removing/replacing the upper. I've never seen one shear off. Maybe it was just a bad part?
Link Posted: 10/20/2003 5:18:05 AM EDT
wgjhsaft, Did the buffer retainer break or did it get pulled out of the hole it sits in? If it broke check the face of your buffer for indents from it. It may have been getting struck by the buffer on each battery stroke. Is the rear of bolt carrier flush with, or slightly above the rear surface of your upper receiver when the bolt is in battery? If it got pulled out of its recess you prolly need to screw your lower receiver extension in another turn. A lot of the cheaper collapsible stocks don't use indexed threads so when they're screwed in far enough to engage the buffer detent they're not in the correct radial orientation or they're screwed in so far they impinge on the upper. Very few of the clone stocks have the extra timing lip that ensures that the buffer detent is engages without interfering with the upper.
Link Posted: 10/20/2003 5:40:09 AM EDT
Originally Posted By Tweak: wgjhsaft, Did the buffer retainer break or did it get pulled out of the hole it sits in?
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The retainer itself broke. The lower portion and the spring stayed in its hole while the portion of the retainer that sticks up to stop the buffer broke off.
If it broke check the face of your buffer for indents from it. It may have been getting struck by the buffer on each battery stroke.
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There are some indentations from it, but they are barely noticable, almost as if the buffer just nicked it while taking it off.
Is the rear of bolt carrier flush with, or slightly above the rear surface of your upper receiver when the bolt is in battery?
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I have to take another look at that to be sure. It doesn't stick out of the upper while in battery if that is what you are implying.
If it got pulled out of its recess you prolly need to screw your lower receiver extension in another turn. A lot of the cheaper collapsible stocks don't use indexed threads so when they're screwed in far enough to engage the buffer detent they're not in the correct radial orientation or they're screwed in so far they impinge on the upper. Very few of the clone stocks have the extra timing lip that ensures that the buffer detent is engages without interfering with the upper.
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The J&T Fake M4 stock does have a little recess in it to hold the retainer in place. When I first built it I did screw the stock in too much, but realized that I did after trying to mate the upper and lower receivers. I have a feeling that it just happens to be a defective part. The rifle fired great otherwise and even fired without it. I will contact J&T to see if they have had similar issues.
Link Posted: 10/20/2003 5:58:26 AM EDT
Originally Posted By wgjhsafT: It doesn't stick out of the upper while in battery if that is what you are implying.
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So the rear of the bolt carrier sits below the rear surface of the upper receiver? Or is the rear of the carrier flush with or slightly above the rear surface of the upper receiver?
Link Posted: 10/20/2003 6:06:03 AM EDT
Originally Posted By Tweak:
Originally Posted By wgjhsafT: It doesn't stick out of the upper while in battery if that is what you are implying.
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So the rear of the bolt carrier sits below the rear surface of the upper receiver? Or is the rear of the carrier flush with or slightly above the rear surface of the upper receiver?
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I'll have to take a look at it. I'm at work now so I won't be able to check until this evening. From memory the carrier sits flush with the upper receiver. After cycling the action and shooting there are marks on the buffer from the carrier that show the carrier is hitting the buffer only. However I will examine it this evening to fully answer your questions. Thanks for your help!
Link Posted: 10/20/2003 11:16:36 AM EDT
It was probably a bad buffer retainer. I can tell you that in my rifle the buffer smacks (well it did, doesn't anymore) the buffer retainer on every firing (EXTREMELY LIGHTLY) but just enough to leave small marks around the outer edge of the buffer. My buffer retainer never broke off or deformed. It came from a Bushmaster lower parts kit. From what I can see now though, the buffer hasn't received any more wear (wore in & stopped) so it was just making mild contact to start with.
Link Posted: 10/21/2003 3:46:25 AM EDT
OK, I took a good look at the whole area in question last night. The bolt carrier sits flush with the uppper receiver, it does not stick out of the receiver in any way. Also, it sits right where it should be in the UR so I doubt that the carrier ran it over (as in was too low). I took the carrier out of the UR and then mated it up against the buffer where it has left marks. I was suprised to see how easily the carrier has marked up the buffer, but that made it easier to see exactly where carrier hits the buffer. I didn't see anything unusual there. My guess is that it was just a bad retainer. I went out and shot last night (the wife let me out!) and put 400 rounds down range. Guess what, nothing broke, the rifle never malfunctioned, the Brit mags I was usuing locked into the gun without a hitch, it was beautiful. Thanks everyone for all of your help!
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